Ha! We did the same thing on our campus to get around the bandwidth blocks. We had an internal file-sharing network (DC++) which wasn't restricted in any way since it was all internal traffic. In fact the server was run by one of the network admins...go figure. But, content has to come from somewhere outside the network, so I just kept a rotating list of about 20 randomly-generated MAC addresses to keep the pipe open at full speed. I mentioned I was doing this to a friend in the IT department at some point, and he said the university knew about the trick and that I should be careful, but nothing ever came of it.

In reality, the real rate-limit was my college budget and the price of hard drives, but it was all good fun.